Improving road and rail networks can have social and economic benefits but also significant environmental consequences on biodiversity and ecosystem services. Weighing the ecological consequences of building and operating transport infrastructure in specific locations against the social and economic benefits that would result is essential for making sound decisions. This study aimed to produce a foundational, globally consistent assessment of the risks and benefits to people and the nature of currently planned, large-scale road and rail transport infrastructure projects. Ultimately this can help to improve regional, national, and global decision making. The study also included the development of a novel global database of planned roads and railways. Detailed results of the analysis can be explored using the Global Infrastructure Impact Viewer (GIIV), a web-based tool that was created for this project.